Major ampullate (dragline) silk of orb web spiders possesses unique physical properties, combining high tensile strength and substantial elasticity, Denny, M. W. J. Exp. Biol., 65, 483-506 (1976); Lucas, F. Discovery, 25, 20-26 (1964). Previous investigations suggest that spider silk is composed of a single large protein, primarily containing pseudo-crystalline regions of stack .beta.-pleated sheet alternating with amorphous domains, Warwicker, J. O., J. Mol. Biol., 2, 350-362 (1960); Lucase, F. et al, J. Text Inst., 46, T440-T452 (1985); Hepburn, H. R. et al., Insect Biochem., 9, 69-71 (1979). The molecular basis for spider silk elasticity is presently unknown, although it has been suggested that an entropy driven process like that found in rubber is involved, Gosline, J. M., et al., Nature, 309, 551-552 (1984). It has also been speculated that the amorphous regions contribute substantially to the elastic properties of the fiber, Hepburn, H. R., et al., Insect Biochem., 9, 69-77 (1979).